[Issue 4725] std.algorithm.sum()

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4725



--- Comment #19 from bearophile_hugs at eml.cc 2013-03-25 10:49:55 PDT ---
Is it worth adding to sum() an optional argument with the start value, as in
the Python sum()?

In this program in the first case there is an array of floats and you want to
use a real sum for max precision. In the second example there is an array of
ints, and the programmer wants to sum inside a long to avoid overflow:


import std.stdio, std.algorithm;

void main() {
    float[] a1 = [1.21, 1.3, 1.4];
    real s1 = reduce!q{a + b}(0.0L, a1);
    writefln("%.19f", s1);
    writefln("%.19f", a1.sum);

    int[] a2 = [int.max, int.max, int.max];
    real s2 = reduce!q{a + b}(0L, a2);
    writeln(s2);
    writeln(a2.sum);
}

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